Apple has given in to intense pressure from Chinese state media about its customer service practices, ________  to consumers in its second-largest market.

A．apologizing

B．apologize

C．having apologized

D．to apologize

近年来，乳酸成为人们研究的热点之一，它在医药、食品等行业中有广阔的应用前景，乳酸的化学式为C₃H₆O₃．试计算：

（1）乳酸中各元素的质量比；

（2）180g乳酸所含氢元素的质量是多少？